In an air-ingesting turbo machine (e.g., a gas turbine), air is pressurized by a compressor and then mixed with fuel and ignited within an annular array of combustors to generate hot gases of combustion. The hot gases flow from each combustor through a transition piece for flow along an annular hot gas path. Turbine stages are typically disposed along the hot gas path such that the hot gases flow through first-stage nozzles and buckets and through the nozzles and buckets of follow-on turbine stages. The turbine buckets may be secured to a plurality of rotor disks comprising the turbine rotor, with each rotor disk being mounted to the rotor shaft for rotation therewith.
A turbine bucket generally includes an airfoil extending radially outwardly from a substantially planar platform and a shank portion extending radially inwardly from the platform for securing the bucket to one of the rotor disks. The tip of the airfoil is typically configured to be spaced radially inwardly from a stationary shroud of the turbo machine such that a small gap is defined between the tip and the shroud. This gap is typically sized as small as practical to minimize the flow of hot gases between the airfoil tip and the shroud.
In many instances, the tip of the airfoil may include a squealer tip wall extending around the perimeter of the airfoil so as to define a tip cavity and a tip floor therebetween. The squealer tip wall is generally used to reduce the size of the gap defined between the airfoil tip and the shroud. However, this creates an additional component of the turbine bucket that is subject to heating by the hot gas flowing around the airfoil. Thus, cooling holes are typically defined in the tip floor to allow a cooling medium to be directed from an airfoil cooling circuit within the airfoil to the tip cavity.
Accordingly, an improved tip configuration that allows for enhanced cooling of an airfoil tip would be welcomed in the technology.